How do you test crank sensor?

Answer 1

Here's how you can test the 4 wire Crank Position Sensor.This is on the GM V6 3300 early 90's.

Use any cheap volt/ohm meter. First test the 12v+ input on the ICM. It is the only red wire on the far left of the ICM plug.

Then make sure you have 12v+ coming back out the white wire w/black stripe. It's in the second position next to the red wire. This is the 12 volt supply going down to the CPS. You can also pull the CPS plug and test the voltage on that end. Both tests need to be with key on; NOT running.

Check to make sure you have a solid ground as well. This is the 3rd from the left wire on the ICM plug. It is black w/white stripe. With the key off, you can check the ground wire continuity. You should have a solid connection between the end of the black wire w/white stripe and the engine. With an oms meter, this means a dead short. It will read "1" (an open is "0").

Put the plug back in the CPS sensor to continue...

Next you can test the 2 loop circuits in the CPS its self using the two wires just to the left and the right of the center screw that holds the plug to the ICM. The light blue w/white stripe is on the left (sometimes discolored with age and looks greenish). The one just to the right is either solid yellow or dark blue w/white stripe depending on exact model's wiring from the factory. I'm pretty sure that all the 3300 Buick's and Olds Cutlass Cierra used dark blue; yellow is on the V8's. If you look down at your PCS you will see the other end of the wire and can confirm the color at the CPS plug. It's in plain sight.

You will see the white w/black stripe wire, the 2 signal wires and the 4th is the ground wire. You can do a continuity test on all 4 wires to make sure you don't have a broken wire in this 2 foot long part of the harness.

Here's the pain in the neck part... Get a 15/16ths socket or metric equivalent and put it on a long breaker bar. Remove the serpentine belt from the crank pulley. You can just leave it loose on the other pullies, you don't need to pull it out. You will turn the crankshaft with the socket on the center nut in the clockwise position while the key is on; NOT running.

With the volt meter you will see a change from Zero to 5 or 6 volts, then back to Zero. This "pulse" is the sensor picking up the slots in the crank rings behind the crank pulley. this sends the signal back to the ICM. Do this for both of the wires on either side of the center retaining screw.

If either "pulse" signal is not there (like, it stays on 0 volts) then you have a defective CPS. Find some changing instructions on the net somewhere and get into it .